The principles of the present invention are applicable to industrial fastener driving tools of the type utilized to drive staples, nails and other fastening means. While not intended to be so limited, the present invention will, for purposes of an exemplary showing, be described in its application to an industrial staple driving tool.
In the manufacture of industrial staplers and nailers, it is common practice to provide a guide body and an associated latchable gate at the lower front nose portion of the tool. The guide body and gate (when the gate is in closed position) define a drive track for the tool driver and for the fastener elements. The purpose of the gate is to provide access to the drive track in the event that a fastener becomes jammed in the drive track.
Prior art workers have devised numerous types of gate and gate latch assemblies. Examples of such structures are taught in U.S. Pat. Nos. 3,273,777; 3,905,535; and 4,139,137.
The prior art gate and latch assemblies, of which the above mentioned patents are exemplary only, have been characterized by certain deficiencies. Force is applied to the gate latch each time a fastener is driven, because the gate is a part of the drive track. This has frequently cuased excessive wear on the latch mechanism. In many prior art structures, the forces required to latch and unlatch the gate are high. When the tool is jammed, as much as a 1.5 ton load may be applied to the gate. The forces required to unlatch the gate frequently becomes so high, when a fastener is jammed in the drive track, that a hammer or other tool is required to unlatch the front gate. This can result in additional damage to the latch mechanism and the tool itself.
In copending application Ser. No. 06/360,180, filed Mar. 22, 1982, in the name of William T. Jobe, and entitled FRONT GATE AND LATCH ASSEMBLY FOR THE GUIDE BODY OF AN INDUSTRIAL FASTENER DRIVING TOOL, there is taught a latch assembly which overcomes many of the above noted deficiencies of earlier latch assemblies. The latch assembly of this copending application, however, is made up of a number of parts, some of which require machining.
The structure of the present invention provides a positive latch which can be easily opened manually, even when a fastener is jammed in the drive track. Latching of the gate is positive by virtue of the over-center action of the latch. Furthermore, the latch assembly of the present invention does not require close tolerance manufacturing.